Pushbutton for solid state wristwatch

ABSTRACT

Disclosed is an improved push button assembly for thedemand switch of a wristwatch having a light emitting diode display. A permanent magnet is mounted inside the pushbutton on a curved leaf spring which forms the return spring for the button. When the button is depressed the spring is deformed moving the permanent magnet close to a reed switch inside the watch case. In this position, the polarization of the magnet is parallel to the reed switch contacts.

United States Patent [191 I OConnor [451 Nov. 18, 1975 PUSHBU'ITON FORSOLID STATE WRISTWATCH Inventor: Arthur H. OConnor, Lancaster, Pa.Assignee: Time Computer, Inc., Lancaster, Pa.

Filed: June 20, 1974 Appl. No.2 481,331

US. Cl. 335/153; 58/50 R Int. Cl. HOlH l/66 Field of Search 58/50 R,85.5; 335/151,

[56] References Cited UNITED STATES PATENTS 9/1965 Deshautreaux 335/153X l/l97l Posey 335/205 2/1974 Bergey 58/85.5 X

6O 5O 58 I6 5 FOREIGN PATENTS OR APPLICATIONS 1,174,890 7/1964 Germany335/153 Primary Examiner-G. Harris Attorney, Agent, or Firm-LeBlanc &Shur [57] ABSTRACT 13 Claims, 6 Drawing Figures V ii" so A w US. PatentNov. 18,1975 Sheet10f2 3,921,108

FIG.| 1

US. Patent Nov. 18, 1975 Sheet 2 of2 3,921,108

FIG.3

FIG. 4

f 50 f N Iz J N S s 70 [f 2/70 28 EEK): 30'

which is incorporated herein by reference, and more particularly to animproved demand button or pushbutton for illuminating the watch'displayelements.

There is disclosed in assignees US. Pat. No.

3,576,099, issued Apr. 27, 1971, a solidstate'wrist- It is therefore oneobject of the present invention to providean improved switch assemblyfor solid state watch in which the optical display is described as aplurality of light emitting diodes which are intermittently energized toassure minimum power consumption and an increasingly long life for thewatch batteryIIm 'I proved watch constructions of this general typeincor porating solid state circuits and integrated circuit techniquesare disclosed in assignees US. Pat. No. 3,672,155 and US. Pat. No.3,803,827, among others.

Each of these Wristwatches is provided with a demand switch forilluminating a light emitting diode digital display when the wearerdesires to ascertain the correct time. The reason for'this is that thelight emitting diodes utilize relatively large amounts of the limitedenergy available from the small wristwatch battery orbatteries relativeto the other watch components and by only displaying time on demand,substantial battery energy is conserved. In this way, it is possible toprovide light emitting diode Wristwatches with two one and one-half voltelectrical power cells having a useful life of well over one year;

In the past, Wristwatches of this type have employed a pushbutton for"actuating the demand switch of the type shown and described in assigneesUS. Pat. No. 3,782,102 issued Jan, 1, 1974. The demand button orpushbutton hasformed movable with it a permanent magnet which, when thebutton is depressed, moves closer'to a magnetic field responsive reedswitch within the watch case to actuate the switch. By incorporating apermanent'magnetvvhich"at all times is placed outside I the case or caseclosure,'all watch case shaft or stem sealing problems" are eliminated.

The present invention is directed to an improved pushbutton assembly fora solid state wristwatch of the type described above and in particularto an improved magnetic circuit construction for the watch displaydemand switch. As contrasted with the previous construction in which thepermanent magnet carried by the demand button is polarizedperpendicularto the plane of the reed switch contacts, in the presentinvention, the permanent magnet carried by the demand button ispolarized parallel to the plane of the reed switch contacts. Thisprovides a simplified and less expensive construction and in particularsignificantly increases the reliability of the operation of the demandswitch by insuring accurate switch closure when the demand button isdepressed and switch opening when the demand button is released by thefinger of the watch wearer.

i An radditional important feature of'the present inven' tion involves anovel mounting arrangement for. the

permanent magnet in the pushbutton assembly where the magnet is carriedby an outwardly projecting tab on a normally curved flat spring or leafspring which pro- .vides return bias for the demand button so as tore'sil- Wristwatches.

.- Another object of the present invention is to provide .animproveddemand switch assembly for Wristwatches having a light emittingdiode display.

Another object ofthe present invention is to provide a light emittingdiode display wristwatch with a demand button having an improvedmagnetic circuit for operating a reed switch within the watch case.

Another object of the" present invention is to provide animprovedpermanent magnet and flat spring construction for the pushbutton of thedemand switch of a light emitting diode solid state wristwatch.

I These and further objects and advantages of the inventionwill be moreapparent upon reference to the following specification, claims andappended drawings wherein:

FIG. 1 is a cross section through the demand switch assembly of thepresent invention with the switch in the open contact position;

FIG. 2 is a cross section through the switch assembly taken along line2.2 of FIG. 1;

FIG. 3 is a cross section similar to FIG. 1 showing the pushbuttondepressed and the reed switch contacts in the switch closed position;

. FIG. 4 is a plan view of the flat spring or leaf spring forming apartof the switch assembly of FIGS. 13;

FIG. 5 is a diagrammatic view of the switch assembly of the presentinvention showing the improved magnetic circuit arrangement; and

.FIG. 6 is a schematic diagram similar to FIG. 5 useful in theexplanation of the improvement.

Referring to the drawings, the novel switch assembly of the presentinvention is generally indicated at 10 in FIG. 1. That FIGURE shows incross section a portion of the wristwatch case 12 in which is provided arectangular aperture 14 slidably receiving a demand button or pushbutton16. The lower end of aperture 14 is stepped to a larger size to providea ledge 18. Its lower end is closed off and permanently sealed by ametal pan 20 which is secured preferably by an epoxy as indicated at 22to the watch case 12.

Suitablymounted on a frame (not shown) inside the .watch case is amagnetic field responsive reed switch 24 comprising envelope 26 and apair of normally spaced contacts 28 and 30. Reed switch 24 is ofconventional construction and electrical connection to the contacts 28and 30 is made through the envelope 26 to a'pair of electrical leads 32and 34. t Located within pan 20 with its outer ends 35 and 36 restingonthe bottom 38 of the pan is an arcuately 'FIG. 4 defining an upwardlyprojecting substantially straight tab 48. Secured to the tab again byepoxy or the like, andcarried by the tab is a rectangular cross sectionpermanentmagnet 50 preferably formed from a "rare earthcobalt such asSammarium cobalt or the like.

The magnet'is polarized to define north and south poles at itsrespective ends 52'and 54..

Permanent magnet 50 is received within a central cavity 56 ofpushbuttonl6 and its uppermost tip 58 in theposition shown in FIG. l just clearsthe top 60 of the pushbutton. Formed integral with the top or cover 3 60of the pushbutton are the downwardly extending sides which terminate inan outwardly extending annular flange 62. This flange in the positionillustrated in FIGS. 1 and 2 engages a resilient sealing ring 64suitably secured to the underside of ledgel8 so as to limit upwardmovement of pushbutton 16'. The pushbutton is urged upwardly by theengagement of a portion of the legs and flange 62 with the leaf spring40 as best seen in FIG. 2.

FIG. 3 is a view similar to FIG. 1, but shows the pushbutton 16depressed by downward pressure on it as indicated by the arrow 70. Inthis position, spring 40 assumes a completely flat position inengagement with the bottom 38 of pan 20 and the magnetic field from thepermanent magnet 50 acts on the contacts 28 and 30 of thereed switch 24to bring them together closing the electrical circuit between electricalleads 32 and 34. The pushbutton 16 is illustrated in FIG. 3 in itsdownward most position which is limited by the bottom of pan 20.

FIGS. and 6 are diagrammatic views illustrating the approximate magneticfields of a permanent magnet adjacent the leaf spring contacts 28 and30. FIG. 5 is a diagrammatic representation of the construction of thepresent invention where the magnet 50 is polarized parallel to theplanes of the reed switch contacts 28 and 30. FIG. 6 shows a similarpermanent magnet 50' representative of prior constructions in which themagnet is polarized perpendicular to the planes of switch contacts 28'and 30. The improved nature of the magnetic circuit afforded by theparallel polarization of the present invention as illustrated in FIG. 5,is apparent from the more uniform nature of the magnetic flux lines 70in passing through the adjacent ends of the contacts 28 and 30 ascompared to the flux lines 70 of magnet 50' in FIG. 6.

The improved magnetic circuit not only decreases the size of the magnetnecessary, but optionally makes it possible to utilize the same sizemagnet if desired, and attain significantly improved operatingcharacteristics for switch closure and opening. This is particularlyfacilitated by the novel leaf spring construction of the presentinvention which brings the magnet in close proximity to the reed switch24 for switch closure but which, at the same time, positively urges themagnet away from the switch causing it to open when the downwardpressure represented by arrow 68 in FIG. 3 is removed. Typical operatingcharacteristics for the switch assembly as illustrated in FIGS. 1 and 2,makes it possible to close the switch with a magnetic field pullingstrength of between approximately 25 and 60 ampere turns and providesfor drop out or switch opening at a value not less than 70 percent ofthe pull in field, i.e., 70-percent of the 25 to 60 ampere turn pull infield. This insures that the reed switch 24 will be closed with aminimum of pressure on the pushbutton 16 and further it insures rapidand positive opening of the reed switch when the pressure is removed.Typically, the demand button 16 is operated by depressing it with theindex finger of the other hand of the watch wearer.

It is apparent that the present invention provides a simplified andinexpensive pushbutton construction particularly adapted for solid statewristwatches having light emitting diode displays where, the display isonly energized when the demand button is depressed. Substantialincreases in reliability of operation are brought about by the parallelpolarization of the permanent magnet and by the automatic and positiveaction of leaf spring 40 in returning pushbutton 16 to its initialposition and, at the same time, by means of the tab or projection 48,positively returning the permanent magnet 50 to its rest position asillustrated in FIG. 1, remote from switch contacts 28 and 30, so thatthe switch contacts are permitted to positively reopen with the magnetwell away from the pull in position.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The presentembodiment is, therefor, to be considered in all respects asillustrative and not restrictive, the scope of the invention beingindicated by the appended claims rather than by the foregoingdescription, and all changes which come within the meaning and range ofequivalency of the claims are therefore intended to be embraced therein.

What is claimed and desired to be secured by United States LettersPatent is: p

l. A wristwatch comprising a watch case, a magnetic field responsiveswitch in said case, said switch comprising a pair of electricalcontacts lying in at least substantially parallel planes, a permanentmagnet mounted on said case in a first position adjacent said switchcontacts where the polarization of said magnet is oriented at an acuteangle relative to the planes of said contacts, and means on said caseresponsive to manual pressure for moving said permanent magnet by bothrotation and translation into a second position closer to said switchcontacts where the polarization of said magnet is at least substantiallyparallel to the planes of said contacts.

2. A wristwatch according to claim 1 wherein said magnetic fieldresponsive switch is a reed switch.

3. A wristwatch according to claim 1 wherein said contacts are normallyspaced and close in the presence of a magnetic field.

4. A wristwatch according to claim 1 including means on said caseresiliently biasing said permanent magnet toward said first position.

5. A wristwatch according to claim 4 wherein said biasing meanscomprises a curved leaf spring.

6. A wristwatch according to claim 5 wherein said leaf spring includes astraight. portion on which said magnet is mounted.

7. A wristwatch according to claim 6 wherein said straight portioncomprises a tab projecting outwardly adjacent the center of said leafspring.

8. A wristwatch according to claim 7 wherein said leaf spring comprisestwo layers, said tab projecting from only one of said layers.

9. A wristwatch according to claim 7 wherein said leaf spring is curvedwith its central portion furthest from said switch contacts.

10. A wristwatch comprising a watch case having an aperture, an invertedcup shaped demand button slidably mounted in said aperture, a supportsecured to said case and closing off the inner end of said aperture,said-button being movable along an axis from outside said case towardand away from said support, a magnetic field responsive switch in saidcase adjacent said support, a curved leaf spring having its convex sidetoward said button resiliently urging said button toward the outer endof said aperture, said leaf spring having a straight portion extendingoutwardly of the remainder of said spring into the hollow cup portion ofsaid button, and a permanent magnet mounted on said straight portion ofsaid spring, said magnet being movable with said spring when said buttonis pressed from a first posi- 'tion remote from said contacts to asecond position ad- 6 and said support.

12. A wristwatch according to claim 11 wherein said spring engages saidbutton flange.

13. A wristwatch according to claim 10 wherein said magnet is comprisedof a rare earth cobalt material.

1. A wristwatch comprising a watch case, a magnetic field responsiveswitch in said case, said switch comprising a pair of electricalcontacts lying in at least substantially parallel planes, a permanentmagnet mounted on said case in a first position adjacent said switchcontacts where the polarization of said magnet is oriented at an acuteangle relative to the planes of said contacts, and means on said caseresponsive to manual pressure for moving said permanent magnet by bothrotation and translation into a second position closer to said switchcontacts where the polarization of said magnet is at least substantiallyparallel to the planes of said contacts.
 2. A wristwatch according toclaim 1 wherein said magnetic field responsive switch is a reed switch.3. A wristwatch according to claim 1 wherein said contacts are normallyspaced and close in the presence of a magnetic field.
 4. A wristwatchaccording to claim 1 including means on said case resiliently biasingsaid permanent magnet toward said first position.
 5. A wristwatchaccording to claim 4 wherein said biasing means comprises a curved leafspring.
 6. A wristwatch according to claim 5 wherein said leaf springincludes a straight portion on which said magnet is mounted.
 7. Awristwatch according to claim 6 wherein said straight portion comprisesa tab projecting outwardly adjacent the center of said leaf spring.
 8. Awristwatch according to claim 7 wherein said leaf spring comprises twolayers, said tab projecting from only one of said layers.
 9. Awristwatch according to claim 7 wherein said leaf spring is curved withits central portion furthest from said switch contacts.
 10. A wristwatchcomprising a watch case having an aperture, an inverted cup shapeddemand button slidably mounted in said aperture, a support secured tosaid case and closing off the inner end of said aperture, said buttonbeing movable along an axis from outside said case toward and away fromsaid support, a magnetic field responsive switch in said case adjacentsaid support, a curved leaf spring having its convex side toward saidbutton resiliently urging said button toward the outer end of saidaperture, said leaf spring having a straight portion extending outwardlyof the remainder of said spring into the hollow cup portion of saidbutton, and a permanent magnet mounted on said straight portion of saidspring, said magnet being movable with said spring when said button ispressed from a first position remote from said contacts to a secondposition adjacent said contacts, said magnet in said second positionbeing polarized perpendicular to the axis of motion of said button. 11.A wristwatch according to claim 10 wherein said aperture is enlarged atits inner end to define a ledge, said button having a flange movablebetween said ledge and said support.
 12. A wristwatch according to claim11 wherein said spring engages said button flange.
 13. A wristwatchaccording to claim 10 wherein said magnet is comprised of a rare earthcobalt material.